Hi Chris,

upstream says that compiling rust 1.19.0 works fine for them on i686 with their mrustc
master (since they have applied our variable-length integer decoding patch):

https://github.com/thepowersgang/mrustc/issues/108

>Hmm... works for me, using gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516 on linux 4.9.0-8-686-pae
>Compiling cargo ran sucessfully.

Would you have some time and a free computer to be able to build rust 1.19.0 with 

  ./pre-inst-env guix build -K -s i686-linux rust@1.19.0

on guix master with the patch below?

My laptop is currently trying to survive the merge of staging to master and keeps
running out of memory if I try to start a rust build in parallel, even with swap.

The patch to use mrustc master is:

diff --git a/gnu/packages/rust.scm b/gnu/packages/rust.scm
index e128bb22b..f2a01ded6 100644
--- a/gnu/packages/rust.scm
+++ b/gnu/packages/rust.scm
@@ -97,17 +97,35 @@
     (package
       (name "mrustc")
       (version "0.8.0")
+      ;(source (origin
+      ;          (method git-fetch)
+      ;          (uri (git-reference
+      ;                (url "https://github.com/thepowersgang/mrustc.git")
+      ;                (commit (string-append "v" version))))
+      ;          (file-name (git-file-name name version))
+      ;          (sha256
+      ;           (base32
+      ;            "0a7v8ccyzp1sdkwni8h1698hxpfz2sxhcpx42n6l2pbm0rbjp08i"))
+      ;          (patches
+      ;           (search-patches "mrustc-0.8.0-fix-use-after-free.patch"
+      ;                           "mrustc-0.8.0-fix-variable-length-integer-receiving.patch"
+      ;                           "mrustc-0.8.0-fix-emulated-i128-multiply-divide.patch"
+      ;                           "mrustc-0.8.0-fix-i128-overflow-handling.patch"))))
       (source (origin
                 (method git-fetch)
                 (uri (git-reference
                       (url "https://github.com/thepowersgang/mrustc.git")
-                      (commit (string-append "v" version))))
+                      (commit "7b6fa5c6e7d6838c2479280dd3f8d14a43c13899")))
                 (file-name (git-file-name name version))
                 (sha256
                  (base32
-                  "0a7v8ccyzp1sdkwni8h1698hxpfz2sxhcpx42n6l2pbm0rbjp08i"))
+                  "0ki5jv76gmvd0q9y2lixzn4xhy1jamba3f77bk8cz2k4ix6yx5z1"))
                 (patches
-                 (search-patches "mrustc-0.8.0-fix-variable-length-integer-receiving.patch"))))
+                 (search-patches ;"mrustc-0.8.0-fix-use-after-free.patch"
+                                 ;"mrustc-0.8.0-fix-variable-length-integer-receiving.patch"
+                                 ;"mrustc-0.8.0-fix-emulated-i128-multiply-divide.patch"
+                                 ;"mrustc-0.8.0-fix-i128-overflow-handling.patch"
+                                 ))))


Also have to make rust@1.19.0 public or use an "-e" expression.

If you don't have time, no worries, I'll eventually get to it.